1. Technical Field
The present invention relates to an inductance element such as a choke coil and to a case that contains the inductance element.
2. Background Art
An inductance element disclosed in JP 08-172019 A or the like has been known as one in which a magnetic ribbon such as an iron base amorphous alloy ribbon is wound around on a core having a hollow part, a lead is passed through the core, and the wound magnetic core is contained in a case.
The inductance element is constructed by a toroidal magnetic core having a magnetic alloy foil strip wound therearound, a case that contains the magnetic core, and a lead which is passed through the magnetic core and the case, and has a structure in which the lead is fixed to a body to be connected which is the surface mounting of a circuit board or the like.
This inductance element thinks of exfoliation prevention from said a body, and a front edge department of an above lead line consists of it to become parallel to the surface of a body.
Also, in the inductance element, it is suitable that a maximum length of a cross section of the lead is 0.8 times to 1.2 times the inner diameter of the magnetic core. In the inductance element, with a state in which the lead is inserted into the toroidal magnetic core, the magnetic core is subjected to heat treatment to produce distortion, thereby fixing the lead to the toroidal magnetic core.
Also, in the above-mentioned publication, it is noted that if a clearance is present between the case and the magnetic core, the magnetic core moves, so that it is necessary to fix the case and the magnetic core using a grease, an adhesive, a resin, or the like.
However, in the above-mentioned conventional technique, consideration is not given to vibration resulting from interaction between a current flowing through the lead and the magnetic core, vibration of the case caused due to the vibration, noises resulting from those vibrations, or the like.
Therefore, in a magnetic wound core around which a magnetic ribbon made of, for example, iron base amorphous metal is wound around on a core, when a current is made to flow through a lead, the magnetic core is excited. Magnetostriction is caused by the excitation, which reliably causes vibration. When the vibration thus caused is in an audio frequency range, there is the case where the vibration is propagated as noise throughout the surrounding area. In addition, when the inductance element is bonded to an object to be bonded such as a circuit board, there is the case where parts in the periphery of the inductance element are vibrated, thereby deteriorating operating characteristics of the object to be bonded.
Thus, consideration has been on the idea of containing the magnetic core in the case to obtain a hermetically sealed structure, thereby cutting off the noise caused in the magnetic core to reduce the outside noise leaked of the case, however, when the inductance element in which the lead is passed through the magnetic core is contained in the case, it is required to provide a manufacturing order in which the case is formed in advance so as to be composed of a plurality of members and the members are combined after the core is contained in the case.
Such bonding of the members is generally conducted by a method using an adhesive, ultrasonic bonding, or the like. Further, the larger the area of a bonding region, the more advantageous the above-mentioned bonding method is, in terms of bonding strengths of the respective members in the bonding.
The area of the bonding region is widened as thicknesses of the members composing the case increase. However, there is a problem in that when the thicknesses of the members are increased, a size of the case is accordingly increased.
The present invention has been made in view of such problems of the conventional techniques. Therefore, an object of the present invention is to, in the inductance element which is provided with the winding type magnetic core and the lead, reduce vibration resulting from a current flowing through the lead or noise leaked to the outside of the element.
Also, another object of the present invention is to, in the inductance element, increase the area of the bonding region of the members composing the case without increasing the size of the case that contains the element.